1. Field of the Invention
This invention pertains generally to the field of exhaust hoods, and particularly to the wall mounted and self-supporting type adapted to fit partially around a source of vapors or fumes.
2. Description of The Prior Art
It is often desired to fully ventilate the fumes arising from commercial kitchen and industrial appliances where ceiling mounted ventilating hoods and fans can not be used because of the height of the ceiling, or because the ventilation from a ceiling mounted hood is inadequate. In addition, ceiling mounted hoods will often produce unacceptable drafts across serving counters in open "display" cooking, and will similarly cause drafts through a pass-through type service window between the kitchen and dining areas. In such situations, ventilating hoods are commonly used which are wall mounted or self-supported and which form a partial enclosure about the appliance. Commonly known as backshelf or countertop hoods, the usual ventilating hood of this type has an exhaust opening at the back of the hood allowing communication with an exhaust chamber from which the exhaust gases are withdrawn by suction provided by a ventilating fan. A single exhaust duct generally leads from the top or back of the hood up to the roof where the exhaust fan is located. Substantial amounts of tempered air in the room in which the hood is located must be withdrawn by the fan in order to provide the necessary withdrawal of the fumes from the area directly underneath the top of the hood. This withdrawal of large amounts of tempered air is wasteful of energy as well as being obviously uneconomical. Moreover, because grease particles and vapors can arise to the inside top wall of the hood, frequent cleaning of the underside of the hood is required in order to prevent build up of grease and dirt in this area.